1. Technical Field
The embodiments herein generally relate to communication systems, and more particularly to the field of interleaving data in orthogonal frequency division multiplexing (OFDM) communication systems.
2. Description of the Related Art
An Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) transmitter employs frequency interleaving to randomize burst error, occurring in the frequency domain, which is mainly caused by multipath distortion or carrier interference. An ISDB-T transmitter employs time interleaving to randomize burst error occurring in the time domain, which is mainly caused by impulse noise or fading interference. Time and frequency interleaving operates on the sequence of I/Q-mapped data carrier values (for the given modulation system) that constitute one OFDM symbol. The interleaved OFDM symbols are used to form an OFDM frame.
For performing frequency and time interleaving, existing ISDB-T receiver architectures use either two separate random access memories (RAMs) for the de-interleavers or a bank of flip-flops for the frequency de-interleaver and a RAM for the time de-interleaver. The total memory size required for frequency de-interleaving is (2×nc×ns) words, where nc is the number of data carriers per one data segment and ns is the number of data segments per one OFDM symbol. The data carriers per data segment may be 96, 192 or 384 depending on the system mode; mode 1, mode 2 or mode 3 respectively.
Time de-interleaving requires a large memory owing to de-interleaver delay buffer and therefore, time de-interleaver designs are RAM based. In RAM based designs, implementation of large number of memory pointers may lead to large number of counters. Such counters are generally implemented as flip-flops leading to a larger de-interleaver area and thereby greater power consumption.